1. Project Summary Mitochondrial dysfunction is an early hallmark of inflammatory bowel disease (IBD). In healthy cells, mitochondria consume nutrients and generate most of the energy. However, in cells from inflamed tissue, less energy is produced by mitochondria, and nutrients are reorganized as building blocks to better support cell survival. To date, extensive studies have been focused on the changes and impact of macronutrients such as glucose and lipids in inflamed tissues, but much less is known about the contribution of micronutrients such as iron to IBD. Iron is essential in mitochondrial generation of reactive oxygen species (ROS), which is important for cell survival. Iron is also needed for mitochondria to produce iron-sulfur clusters (ISC) that support many critical cellular processes including tricarboxylic acid (TCA) cycle. The long-term goal is to understand how iron interacts with mitochondria and contributes to the disease progression of IBD. The candidate hypothesizes that mitochondrial iron is a critical mediator for the IBD development by regulating TCA cycle and ROS production. There have been several hurdles that have made understanding the effects of mitochondrial iron on the intestinal inflammation difficult to study, namely appropriate cell and animal models. Here the candidate proposes to utilize a set of unique models: 1) enteroids that keep an intact iron transport system and inflammatory response; 2) a novel transgenic mouse model with intestinal epithelium-specific overexpression of a ferrireductase six transmembrane epithelial antigen 4 (STEAP4), which has enhanced mitochondrial iron accumulation and increased susceptibility to colitis; 3) a novel and highly clinic-relevant humanized Il10-/- mouse model of chronic colitis. The candidate will focus on the following specific aims: 1) Characterize the effect of iron on mitochondrial metabolism in IBD; 2) Understand the role of STEAP4 in mitochondrial iron homeostasis in IBD; 3) Characterize if mitochondrial iron dysregulation contributes to IBD-associated dysbiosis. Accomplishing these goals will provide a mechanistic explanation and novel targets for prevention or treatment of IBD. Aim 1 in the proposal will build upon the strengths and interests of the mentors? laboratories with respect to iron metabolism in the intestine. Moreover, accomplishing Aim 1 will allow the adequate training to utilize the novel enteroids to study the impact of mitochondrial iron on TCA cycles and the utilization of iron. This will aid the transition of the candidate?s research career toward an independent investigator position. Accomplishing Aims 2 and 3 will allow the candidate to understand the role of the ferrireductase STEAP4 in intestinal epithelial biology and the interaction of host mitochondrial micronutrients with the gut microbiota. Together, this proposal is not only critical for the candidate?s career development in the field of micronutrient metabolism and gut microbiota research, but also it will aid in understanding the pathogenesis of IBD.